• Ouf, Mohamed Elsadek

Abstract

xperimental study was carried out on a sample of a clay soil selected from Al-Marg district, Cairo, Egypt to represent atypical Egyptian expansive clayey soil. Modified proctor, unconfined compressive strength (U.C.S) and free swelling (swelling%) testshave been used to evaluate using hydrated lime and Nano slag (N.S) as stabilisers on the compaction characteristics, strength andswelling properties of soils. The results revealed that UCS of the test soil generally increased with an increase in the total binder (T.B%),increased with an increase in curing period and also increased with an increase in N.S/T.B ratio up till a specific value and thendecreased. The swelling% decreased with an increase in the T.B%, decreased with an increase in curing period and also decreased withan increase in N.S/T.B ratio up till a specific value and then decreased. The optimum ratio of N.S/T.B which gives the maximum U.C.Sand minimum swelling%, was found to be between (0.15 and 0.30).Keywords: Stabilisation, Clay, Nano slag, lime, swelling soil. 1. IntroductionThe typical cross section of an Egyptian road pavement is 20 to 30 cm of granular base courses made of compacted wellgraded crushed stone, covered by one or more layer of asphalt concrete (Abdelkader, 1981). This pavement systemis not suitable for a subgrade of expansive clays as it cannotwithstand the effects of the movement of the subgrade, andreplacement of the expansive clay by granular materialswould necessitate extra material being imported thusincreasing the cost of construction on expansive soils. To suppress swelling and reduce volume change and to increasethe strength of expansive clay soils and thus decrease therequired thickness of the sub-base or base layers,stabilisation of these types of soil is necessary.Since the development of soil stabilisation technique in the1960s, many additives have been used such as lime andordinary Portland cement, Sargent (2015).Dolomitic lime, fly ash, steel slag and conventional limehave been used in soil stabilisation. Results showed greaterchanges in clay properties and dolomitic lime can be as effective as commercial lime in soil stabilisation, while thefly ash was found to be the least effective additive, SolSánchez et al (2016). Yaolin Yi et al (2015) evaluated usingmagnesia (MgO) and slag to stabilise a natural clay soil in comparison to Portland cement (PC) using X-ray diffraction(XRD), scanning electron microscopy (SEM), andunconfined compressive strength (UCS) test. The resultsindicated that the main hydration products of slag stabilisedsoil included calcium silicate hydrates (CSH), calciumaluminate hydrates (CAH), and ettringite. For MgO-slagstabilised soils, CSH was the only hydration productdetected.This paper studies the effectiveness of alkaline activation of low-calcium fly ash on the improvement of residual graniticsoils to be used on rammed-earth construction. Differentliquid: solid ratios, alkali concentrations and Na2O:ash ratioswere tested. Effect of calcium hydroxide, sodium chlorideand concrete superplasticiser is also reported. Compressivestrength up to 7 days at 60 °C was determined. Results showthat there is an optimum value for the activator: solids ratioand the alkali concentration, and that a decrease in theNa2O:ash ratio results in a strength increase, Nuno Cristeloet al (2012).Modarres and Nosoudy, (2015) evaluated the effects of coalwaste and hydrated lime on the stabilization of a plastic claypowder. California bearing ratio (CBR) along with swellingand unconfined compressive strength tests were carried out.The addition of coal waste enhanced the soil strength, andthe addition of lime resulted in considerably higher CBR.The results of X-ray diffraction and SEM analyses indicatedsubstantial changes in the soil structure after adding theadditives. The initial structure of the soil was porous andflaky which transformed to a solid and coherent structureafter treating with the it

Topics

• porous
• impedance spectroscopy
• polymer
• scanning electron microscopy
• x-ray diffraction
• strength
• steel
• Sodium
• cement
• activation
• Calcium
• curing
• lime